The present invention relates to a measuring device and method and, more particularly, to a measuring device and method for enabling an evaluation of a moldability of a thermosetting resin by determination of parameters suitable for high accuracy forecasting of flow and curing behaviors of a resin within a metal mold, as well as a metal mold for molding a thermosetting resin and method for constructing runners of the metal mold which is effective to minimize if not prevent the occurrence of faults in moldings.
In, for example, Japanese patent laid open no. 59-88656, an apparatus is proposed wherein an average apparent viscosity in a predetermined section in a flow passage of a metal mold is actually measured.
In accordance with the above proposed arrangement, apparent flow and curing characteristic values in given conditions of dimensions of a flow passage of a metal mold and given molding conditions are determined; however, a forecasting of a flow in a metal mold having a flow passage of differing dimensions cannot be accomplished because the proposed arrangement is incapable of determining parameters peculiar to a resin which is not influenced by such conditions.
Moreover, as a practical problem, providing or constructing a metal mold having a flow passage which has the nearest possible dimensions to dimensions of a metal mold capable of being mass produced results in high production costs for the metal mold.
In, for example, Japanese publication no. 55-17697, a method of designing runners of a metal mold having a plurality of mold cavities for molding a thermosetting is proposed wherein a runner of the molten thermosetting resin is formed so that the depth of the runner decreases gradually toward an extremity thereof, with a restriction angle of a gate for a mold cavity furthest from a mold receiving pot being greater than that of a gate for a mold cavity nearer to the mold receiving pot whereby a sum of pressure losses in the runner and gate is the same for all mold cavities.
A disadvantage of the last proposed method resides in the fact that the method disregards the estimating of a flow mode of the resin which flows through a runner having a complicated shape while the temperature and viscosity of the resin vary. Consequently, it is extremely difficult to charge all of the mold cavities of the metal mold at equal charging rates. Therefore, any possible improvement in the quality of the products molded in a metal mold produced in accordance with this proposed method is extremely limited.
In a paper entitled "Simulation of Balanced Filling in a Multi-Cavity Mold for Encapsulation of Semiconductor Device", J. Saeki and A. Kaneda, Processing Society Meeting, May 8-11, 1988, a method for analyzing mold filling dynamics through a channel of circular cross-section is proposed which examines viscosity and enables a quick and accurate evaluation of rheological properties of commercial molding components by a data measuring and analyzing apparatus.
A disadvantage of the last mentioned method and apparatus resides in the fact that the proposed data measuring and analyzing apparatus does not take into account various parameters unique to particular thermosetting resins and, consequently, the proposed techniques do not permit an optimization of a metal mold construction which is readily reproducible and ensures production of fault free molds.
In, for example, an article entitled "Simulation of Balanced Filling in a Multi-Cavity Mold for Encapsulation of Semiconductor Device", Nikkei Microdevices, vol. 6, 1988, pps. 95-102, a transfer molding method and apparatus is proposed which decreases the costs and necessary developing for producing a plastic molded package for an LSI.
While the technique proposed in the last mentioned publication can reduce void defects in a mold to about one-third and reduce distortion of a gold lead to about one-fifth of other conventional proposals, the proposed techniques are ineffective since such techniques do not take into consideration non-isothermal viscosity behavior of a thermosetting resin nor take into account unique or peculiar parameters of a particular resin. Consequently, the last mentioned proposal does not provide a total solution to optimize the quality of the products molded in a metal mold since the proposal does not recognize nor utilize unique flow and curing parameters of particular thermosetting resins being employed in the molding process.